CVE-2020-19316
📋 TL;DR
This CVE describes an OS command injection vulnerability in Laravel's Filesystem.php link function. It allows attackers to execute arbitrary operating system commands on the server by manipulating symlink creation. All Laravel applications using the affected framework versions are vulnerable if they use the link() method.
💻 Affected Systems
- Laravel Framework
📦 What is this software?
Framework by Laravel
⚠️ Risk & Real-World Impact
Worst Case
Full server compromise allowing remote code execution, data exfiltration, lateral movement, and complete system takeover.
Likely Case
Arbitrary command execution leading to web shell installation, data theft, or service disruption.
If Mitigated
Limited impact due to proper input validation, restricted permissions, and network segmentation.
🎯 Exploit Status
Exploitation requires attacker to control input to the link() method. Public proof-of-concept demonstrates command injection.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 5.8.17
Vendor Advisory: https://github.com/laravel/framework/commit/44c3feb604944599ad1c782a9942981c3991fa31
Restart Required: No
Instructions:
1. Update Laravel framework to version 5.8.17 or later. 2. Run 'composer update laravel/framework'. 3. Test application functionality.
🔧 Temporary Workarounds
Input Validation
allImplement strict input validation and sanitization for all parameters passed to the link() method.
Method Avoidance
allAvoid using the vulnerable link() method in Filesystem.php until patched.
🧯 If You Can't Patch
- Implement web application firewall (WAF) rules to block command injection patterns.
- Restrict filesystem permissions and run Laravel with least privilege user accounts.
🔍 How to Verify
Check if Vulnerable:
Check Laravel version in composer.json or run 'php artisan --version'. If version is below 5.8.17, check if application uses Filesystem::link() method.Check Version:
php artisan --versionVerify Fix Applied:
Confirm Laravel version is 5.8.17 or higher using 'php artisan --version'. Review code to ensure link() method calls are properly validated.📡 Detection & Monitoring
Log Indicators:
- Unusual symlink creation attempts
- Command execution patterns in application logs
- Filesystem permission errors
Network Indicators:
- Unexpected outbound connections from web server
- Suspicious POST requests with shell commands
SIEM Query:
source="laravel.log" AND ("symlink" OR "link()" OR "exec(" OR "system(")🔗 References
- http://www.netbytesec.com/advisories/OSCommandInjectionInLaravelFramework/
- https://github.com/laravel/framework/commit/44c3feb604944599ad1c782a9942981c3991fa31
- http://www.netbytesec.com/advisories/OSCommandInjectionInLaravelFramework/
- https://github.com/laravel/framework/commit/44c3feb604944599ad1c782a9942981c3991fa31
